Feed mechanism for sewing machines



Feb. 17. 1925. 1,526,937

R. M. SHARAF v FEED MECHANISM FOR SEWING MACHINE;

Filed ya! 4, 1921 Jmv my.

Patented Feb. 17, 1925.

UNITED STATES PATENT OFFICE.

RALPH M. SHARAF, OF NEW YORK, N. Y., AS'SIGNOR TO B. M. SHARAF MACHINE COMPANY, OF BOSTON, MASSACHUSETTS, A CORPORATION OF MASSACHUSETTS.

FEED MECHANISM FOR SEWING MACHINES.

Application filed May 4, 1921.

To all whom it may concern.

Be it known that I, RALPH M. SHARAF, 1 a citizen of the United States, and resident of the borough of Bronx, county of Bronx,

cation primarily contemplates certain improvements in a feeding mechanism for machines of the character referred to, of that type disclosed in a second application for patent filed by me on December 11,1917, Serial No. 206,694. It is, however, to be understood that these improvements are not necessarily limited in their utility to application and use in connection with any specific type of sewing machine, though they may perhaps find their greatest utility when employed in combination with the mechanism disclosed in my co-pending applications.

It is one of the important objects of the present invention to provide in a single dog type of feeding mechanism automatically acting means for at all times holding the material against the underside of the vertically movable presser foot and to thereby insure exactly the required extent of feeding movement of the material in each op-.

eration of the feed mechanism for the proper formation of the stitches. V

The present invention further comprehends the provision of improved means for yieldably mounting the feed dog so that in the event that the material engaged by the dog may be thicker at one point than at another, the dog in such event will automatically yield while maintaining a proper gripping action upon the material to insure its movement in the progressive formation 5 of the line of stitching.

Vith theabove and other objects in view,

. the invention consists in the improved feed IHGChBJIISIH for" sewing machlnes and in the Serial No. 466,718.

form, construction and arrangement of the several parts thereof, as will be hereinafter more fully described, illustrated in the ac companying drawings and subsequently incorporated in the subjoined claims.

In the drawings, wherein I have disclosed one practical and satisfactory embodiment of the invention and in which similar reference characters designate corresponding parts throughout the several views:

Figure 1 is a top plan view of the throat plate of a sewing machine, the feed dog being omitted;

Figure 2 is a vertical sectional view through the presser foot and the throat plate taken on the line 2-2 of Figure 1;

Figure 3 is a similar view, the throat plate being partly broken away showing the feed dog in place with the operating means therefor illustrated in dotted lines;

Figure l'is a transverse sectional view taken on the line 4l of Figure 3;

Figure 5 is a longitudinal section taken on the line 55 of Figure 3; and

Figure 6 is an enlarged sectional view of the feed dog.

Referring in detail to the drawings, 5 designates the throat plate of a sewing machine which is provided with spaced parallel longitudinally extending slots 6. The upper surface of the throat plate is also pro vided with longitudinal channels 7 communicating with the respective slots 6 at one of their ends. In these channels 7 the spring steel strips 8 are arranged, the outer ends of said strips being flush with the surface of the throat plate and rigidly fixed to said plate by means of the screws 9. The underside of each of said spring metal strips is recessed as at 10 and the remaining portion of the metal strip extending inwardly from the recess is sprung upwardly as at 11 and owing to the inherent resiliency of the metal is normally projected at its extremity above the upper surface of the throat plate. The inner opposed edges of these free end portions of the resilient metal strips are obliquely inclined as at 12, said inclined edges overlying the slots 6. \Vith these inclined edges 12 of the metal strips 8 the movable material folding members 13 co-operate.

The folders 13 are carried by the presserfoot 1 1- which is mounted upon the lower end of a vertically reciprocating rod .5. Tho [)tttttttttttl. oonntngiotion oi on I I a presser-ioot and the operating mechanism for the folders 13 is fully described and claimed in my co-pending application for patent, Serial No. ,283,4 7 1,-filed MayQ, 1918, and since it forms no essential part of the present invention, need not be herein further described in detail. For the purpose of the present explanation it will sutii'ce to state that the spaced needles 16 of the sewing machine operate through the presserfoot and the slots 6of the throat plate and are vibrated transversely in the guide loops 18 formed on the end of the arm 17 fixed to the underside of the throat plate.

Adjacent to each of the slots .6 and in longitudinal alignment therewith the openings 19 are formed in the throat plate. Be-

neath these openings the longitirdinally movable feed dog is mounted. As herein shown, I preferably form this dog from a metal plate having spaced parallel portions 20 the upper surfaces of which are toothed or corrugated as at 21, the said portions of the feed dog engaging through the respective openings 19 in the throat plate. The portions 20 of the feed dog are integrally connected with each other by means of the cars 22 which extend at right angles to the portions 20 and are pivotally mounted as at 23 upon an oscillatable. head 25L arranged upon the upper end of a fixed stud bolt 25 carried by the longitudinally shiftable yoke 26. The pivots 3 of the feed dog extend substantially in line with the yoke 26. The operating mechanism for oscillating the ea 2s arrying he feed dog n horizontal plane is indicated at 27 and is fully described and claimed in my co-pend ing patent application, Serial No, 206,694 above referredto. A s also disclosed in said application the yoke 26 is longitudinally reciprocated to feed. the work by a crank arm 28 and is vertically moved to project the feed dog through the openings 19 by means of a second arm 29 which oo -acts with the yoke 26. From the foregoing it will be understood that the feed dog comprising the portions 20 is mounted to oscillate in a direction at right angles to the line of. movement of the material.

The feed dog is normally yieldingly supported against pivotal movement upon the head 24; with the portions 20 of the dog in parallel relation to said head by means of a bowed leaf. spring 30, the central portion of which is pivotally engaged upon a pin 3,1 fixed in the head of thebolt 2 5. The tremitiest of this leaf spring respectively bear against the undersides of; the spaced portions 20 of the dog. It will be apparent that in the horizontal oscillating movement of the head 24: the dog, and. itssupporting foot :142.

In the operation ot the inoohnninn no atone described, it Wilt tennoteretooit that the material is drawn over the surface of the throat-plate andiovcr the upwardly projecting end portions of the spring metal strips 8 between said strips and the presser- These strips of spring metal serve to at all times hold the material closely against the underside of the presser-foot and when the resser-foot descends the up wardly projecting ends of'the spring .Inetal strips are forced downwardly and placed under .greater tension. Thus the material is securely held when the feed dog is in lowered position. In .the feeding operation, the dog is moved upwardly so that the portions 20 thereof are projected through the openings 19 in the throat plate and the teeth .or corrugations 21 are caused to grip the material. In this gripping action of the feed dog and during its longitudinalmovement to feed the materiallongitudinal ly over the throat plate,said material is still closely held against the underside of the presser-foot. By reason of the provision of the resilient metal strips 8, the material is fed very accurately to the precise extent necessary in order that the stitches may be properly formed.

As shown in Figure 4 of thedrawings, should the material along one of the lines of stitching be of greater thickness than along the other line of. stitching, the feed dog will readily yield against the holding action of the leaf spring30, said dog rocking upon the pivots 23. It will thus be apparent that both of the parts 20 of the feed dog will in thismannerbe maintained in gripping contact with the material so that the material along both lines of stitching will be fed precisely to the same extent in each operation of the feeding mechanism.

From the foregoing description, considered in connection with the accompanying drawings, the construction, manner of operation and several advantages of the present invention will be clearly understood. I have found that the improvements herein disclosed though of a very simple character greatly increase theaccuracy of the sewing operation as performed by the mechanism. disclosed in my prior applications. By the provision of, the resilient holding means for the material and the improved mounting oli the feed dog, unavoidable contingeiuzies which may affect the uninterrupted coutinuity of the sewing operation will be automatically compensated for.

I have herein disclosed what I consider a preferable embodiment; of the present improvements, but it will of course beunderstood, that the invention-might also; be incorporated in various other alternative structures and I accordingly reserve the privilege of adopting all such legitimate changes in the form, construction and rela tive arrangement of the several elements as may be fairly embodied within the spirit and scope of the invention as claimed.

I claim: 1

1. In a sewing machine, the combination with a throat plate having a groove in its upper surface and a presser foot, of a. leaf spring mounted in said groove for yieldingly holding the material against the underside of the presser foot in all positions of the latter, and means for feeding the material against the retarding action of said spring.

2. In combination with the throat plate, presser foot and needle of a sewing machine, a spring element fixed to the throat plate and having a free end portion normally p-rojecting above the surface of the throat plate and acting to yieldingly hold the material against the underside of the presser foot, said spring element being formed at its free end portion with an inclined edge converging with relation to the other edge of the element to a point adjacent to the path of movement of the needle and said free end portion of the element being arranged to be depressed into the plane of the throat plate upon the downward movement of the presser foot, means for feeding the material against the retarding action of said spring when the presser foot is raised and means co-operating with the inclined edge of said element to fold the edge of the material.

3. In combination with the throat plate and presser foot of a two-needle sewing machine, spring metal strips fixed at one of their ends in the throat plate, the other ends of said strips normally projecting above the surface of the throat plate and yieldingly engaging the material along the respective seam lines thereof to hold the material against the underside of the presser foot, said spring strips being depressed into the plane of the throat plate in the downward movement of the presser foot, and means for feeding the material against the retarding action of said spring strips when the presser foot is raised.

4. In a feed mechanism for two-needle sewing machines, a feed dog having integral spaced portions to grip the material along the respective lines of stitching, and means for mounting said dog whereby the spaced portions thereof may be automatically varied to accommodate themselves by variations in thickness of the material.

5. In a feed mechanism for two-needle sewing machines, a feed dog mounted to oscillate in a direction at right angles to the line of movement of the material and having rigidly connected spaced portionsto grip the material along the respective lines of stitching, and means for yieldingly resisting the oscillating movement of the feed dog and permitting the spaced portions of the dog to automatically accommodate themselves to variations in thickness of the ma terial. r

6. In a feed mechanism for tWo-needl sewing machines, a feed dog pivotally mounted for oscillatory movement in a direction at right angles to the line of movement of the material and having rigidly connected spaced portions to grip the material along the respective lines of stitching, and a spring co-acting with the spaced portions of the dog and yieldingly resisting such oscillating movement, while permitting said spaced portions toautomatically accommodate themselves to variations in thickness of the material.

7. In a feed mechanism for two-needle sewing machines, a longitudinally reciprocating head mounted to oscillate upon a vertical axis, a feed dog pivotally mounted upon said head for oscillatory movement with respect thereto in a direction at right angles to the line of movement of the material, said dog having rigidly connected spaced portions to grip the material along the respective lines of stitching, and means yieldingly resisting such independent oscillating movement of the feed dog while permitting the spaced portions thereof to automatically accommodate themselves to variations in thickness of the material.

8. In a feed mechanism for two-needle sewing machines, a longitudinally reciprocating head mounted to oscillate upon a vertical axis, a feed dog pivotally mounted upon said head for oscillatory movement with respect thereto in a direction at right angles to the line of movement of the ma terial, said dog having rigidly connected spaced portions to grip the material along the respective lines of stitching, and a leaf spring engaged at its ends with the spaced parts of the feed dog and movable as a unit With said dog and the head in the oscilla tion of the latter, said spring yieldingly resisting the independent oscillating movement of the dog while permitting the spaced portions thereof to automatically accommodate themselves to variations in thickness of the material.

9. In a feed mechanism for two-needle sewing machines, an oscillating feed dog having rigidly connected portions at opposite sides of its center of oscillation to grip the material along the respective lines of stitching, and means for resisting the oscillating movement of the feed dog and permitting the spaced portions of the dog to automatically accommodate themselves to variations in thickness of the material.

10. In'fa feed. mechanism for two-needle selves to variationsin thickness of the masewingzmaqhifis, an oscillating feed (1 ogihzwk te-riaL ing; integral gripping portions on ei'chisic lez In testimony that I claiinthe fo'rgoi ng 10 of itspivotalconnectidn andimean s for re as my invention, I have signed my name 8' sisting thefoscillating movment of the rfedf hereunder:

dog and permitt-ing:the spaced portidns of: V I the dog to automatically accommodate them RALPH M. SHARAF. 

